Mac 10.14 + A 3.5.37: It’s a good feature, that A grays out not accessible files: thank you. One little problem here: my files are on an external HDD. When the HDD is not connected, all tracks are gray - as far as good. When I connect the HDD, A scans the library but the tracks - now available - still stay gray. I have to restart A to play music.
I kind of have the same problem, but a little different. I use the “2nd method: iTunes Library Synchronization” to manually update my Audirvana database.
A lot of the songs are greyed out, but still playable. If I rebuild the Audirvana database from scratch then no songs are greyed out - until I synch again.